[Volume 1]. GMAT official guide. 2020 : the definitive guide from the makers of the GMAT exam
[volume 2]. GMAT official guide verbal review. 2020 : get extra practice in addition to the GMAT official guide 2020
[volume 3]. GMAT official guide quantitative review. 2020 : get extra practice in addition to the GMAT official guide 2020.